cpufreq: pxa2xx: initialize variables

cpufreq: pxa2xx: initialize variables

gcc-3.8 correctly found that the variables set by find_freq_tables()
are not initialized if this function is called on something other
than a pxa2xx or pxa3xx:

pxa2xx-cpufreq.c: In function 'pxa_verify_policy':
pxa2xx-cpufreq.c:272:6: warning: 'pxa_freqs_table' may be used uninitialized in this function [-Wmaybe-uninitialized]
pxa2xx-cpufreq.c: In function 'pxa_set_target':
pxa2xx-cpufreq.c:345:23: warning: 'pxa_freq_settings' may be used uninitialized in this function [-Wmaybe-uninitialized]

Rather than adding a bogus initialization that would let us
get a little further before crashing, add an explicit BUG().
We know that this code is designed to run on only these cpus,
so this will fix the build warning and give a more helpful
diagnostic if the code ever changes to run on other machines.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>